Identification of the mechanisms for the development of oligodendrocytes in the zebrafish central nervous system

摘要

Time-course changes in neuronal proliferation and incorporation in avian, amphibian and mammalian brains This comparative interclass study was designed to determine neurogenic compartments in the amphibian, avian and mammalian brains and to determine time-course changes in neurogenic activ- ity in each compartment. The African clawed frog, Japanese quail and BALB/c mouse brains were studied immunohistochemically. In the Japanese quail, proliferating cells were observed mainly in the olfactory ventricular lining, telencephalic ventricular zones and cerebellum. Neuroblasts were incorporated into the olfactory bulb, telencephalon and cerebellum. The density of proliferating cells and neuroblasts in all brain areas declined with post-hatching age. In the BALB/c, proliferating cells were mainly observed in the olfactory bulb, rostral migratory stream, sub ventricular zone of the lateral ventricle and the sub granular zones of the dentate gyrus. Neurob- lasts were observed in similar brain regions as the proliferating cells except for the cerebellum and tectum. The numbers of both prolif- erating and newly formed cells sharply decreased with increasing age in all the neurogenic areas of the BALB/c mouse brain. In the African clawed frog, proliferating cells were observed mainly in the ventricular linings of the olfactory bulb, telencephalon, ven- tral hypothalamus, preoptic region and metencephalon adjacent to the cerebellar granule cell layer. Newly formed cells were observed in the parenchyma of the olfactory bulb, telencephalon, ventral hypothalamus and cerebellum. In all the quantified areas of the post-metamorphic brain of the African clawed frog, the numbers of proliferating and newly formed cells declined with increasing age. It appears that the ventricular lining is the birth site of neurons stud- ied. Similarly, neuronal incorporation is more widespread in the amphibian and avian brains compared to the mammalian brain. It therefore appears that as vertebrates evolve, there is a reduction in the number of brain regions incorporating new neurons. In addi- tion, this work also revealed that neurogenesis decreases with age in all the vertebrates studied.